Washington -LRB- CNN -RRB- -- The U.S. government shut down at 12:01 a.m. ET Tuesday after lawmakers in the House and the Senate could not agree on a spending bill to fund the government .

The two sides bickered and blamed each other for more than a week over Obamacare , the president 's signature health care law . House Republicans insisted the spending bill include anti-Obamacare amendments . Senate Democrats were just as insistent that it did n't .

Federal employees who are considered essential will continue working . But employees deemed non-essential -- close to 800,000 -- will be furloughed .

Most furloughed federal workers are supposed to be out of their offices within four hours of the start of business Tuesday .

President Barack Obama issued a statement early Tuesday to military members and Department of Defense employees about the outcome of the shutdown .

`` Those of you in uniform will remain on your normal duty status , '' the president said . `` Congress has passed , and I am signing into law , legislation to make sure you get your paychecks on time . And we 'll continue working to address any impact this shutdown has on you and your families . ''

`` To all our DOD civiliansâ $ '' I know the days ahead could mean more uncertainty , including possible furloughs , '' the president added . `` And I know this comes on top of the furloughs that many of you already endured this summer . You and your families deserve better than the dysfunction we 're seeing in Congress . ... That 's why I 'll keep working to get Congress to reopen our government and get you back to work as soon as possible . ''

The final hours

The shutdown appeared inevitable Monday night as House Republicans acknowledged they could n't overcome Senate objections to a proposal that includes provisions aimed at derailing Obamacare .

They planned to have another vote overnight that would request a conference with the Senate to work out their differences . But the move , which would not have averted a shutdown , was dismissed by Senate Majority Leader Harry Reid .

`` We will not go to conference with a gun to our head , '' Reid said .

Democratic Rep. Chris Van Hollen said the reason there was n't a budget deal is because Republicans refused to negotiate months ago .

`` They want to go to conference with 45 minutes left , '' Van Hollen said late Monday night . `` That is a recipe for a government shutdown . ''

Legislative ping pong

For the second time Monday , the Senate rejected a House Republican effort to derail Obamacare by linking it to a proposal that would avert the shutdown .

The Senate voted to table House amendments that would have delayed the individual mandate in the health care law and eliminated health insurance premium subsidies for members of Congress , their staffs and the president .

In the latest volley of legislative ping pong over a short-term spending plan needed to avoid the shutdown , House Republicans were expected to meet to discuss their next steps .

Earlier , Senate Democrats had rejected a House proposal by a 54-46 vote , strictly along party lines .

Obama made a previously unscheduled statement to reporters on Monday afternoon , blasting the attempts by House Republicans to undermine Obamacare that he said threaten to harm the economy with a shutdown .

`` You do n't get to extract a ransom for doing your job , for doing what you 're supposed to be doing anyway , where just because there 's a law there that you do n't like , '' the president said .

Obama later called Boehner and other party leaders in the House and Senate , the White House said , but a Boehner spokesman indicated there was no breakthrough .

Moderate GOP revolt against Boehner ?

GOP sources told CNN that moderate House Republicans were trying to galvanize what would amount to a rebellion against Boehner and their tea party colleagues by defeating the latest proposed spending plan with attached anti-Obamacare provisions .

However , a procedural vote on the measure passed with only six Republicans voting `` no . ''

Without congressional approval of new spending legislation , parts of the federal government will begin shutting down when the current fiscal year ends at midnight , forcing agencies to furlough thousands of workers and curtail some services until there is a resolution .

`` I feel sad about it . We expect more from our Congress , '' said Vick Temple , a worker for the Federal Aviation Administration who said he faced being furloughed in a shutdown .

Polls show public opposition to a shutdown , and stocks ended lower Monday on Wall Street due to concerns over the economic impact .

The blame game

Republican Rep. Renee Ellmers of North Carolina said on CNN 's `` New Day '' that her party continues to be deeply concerned about Tuesday 's scheduled opening of Obamacare health insurance exchanges and `` keeping the checkbook out of Barack Obama 's hands and the damage can be done there . ''

Get up to speed on the showdown

Rep. Debbie Wasserman Shultz , D-Florida , appearing alongside Ellmers , characterized the Republican strategy of tying overall government operations to at least a delay in health care changes as `` irrational . ''

`` It jeopardizes the economy and it makes no sense , '' she said .

Weeks of hot potato

Last week , the Senate voted down a House GOP plan to eliminate funding for Obamacare in a short-term spending plan to keep the government running in the new fiscal year that begins Tuesday .

Democrats have pressured Boehner to give up a losing fight over Obamacare forced by tea party conservatives and instead hold a vote on a `` clean '' spending plan that includes no provisions seeking to undermine the health care reforms .

Wasserman Schultz predicted that such a measure would pass easily with support from all Democrats and more moderate Republicans .

Some Republicans expressed frustration Monday with the tactics of their congressional colleagues . Veteran GOP Sen. John McCain of Arizona noted that any attempt to repeal Obamacare would fail because of Obama 's veto , which would require a two-thirds majority in the Senate to overcome .

`` There 's not 67 votes in the United States Senate , therefore , ergo , we 're not going to repeal Obamacare , '' McCain said . `` OK ? That 's it . We may do this for a day . We may do it for a week . We may do it for a month . It 's going to end up the same way . ''

GOP Rep. Charlie Dent of Pennsylvania told CNN Chief Congressional Correspondent Dana Bash that whichever party was to blame , a shutdown will make everyone look bad .

10 ways the shutdown would affect you

Obamacare still a GOP focus

Obama and Democrats reject what they call Republican efforts to use the threat of a government shutdown to force negotiations on the president 's signature health care reforms .

Noting that the 2010 Affordable Care Act has been upheld by the Supreme Court , they say it is settled law that voters endorsed last year by re-electing Obama over GOP candidate Mitt Romney , who campaigned on repealing it .

A new CNN/ORC poll shows that Americans are not happy about the prospect of a shutdown , which is happening because Congress has been unable to pass a budget for the new fiscal year that begins Tuesday .

A game of chicken between Dems , GOP

According to the poll , 68 % of Americans think shutting down the government for even a few days is a bad idea , while 27 % think it 's a good idea .

And it appears most Americans would blame congressional Republicans for a shutdown : Sixty-nine percent said they agreed with the statement that the party 's elected officials were acting like `` spoiled children . ''

Democrats , however , were n't far behind : Fifty-eight percent of respondents said they too were acting like spoiled kids .

A poll later showed public support for Congress at record low levels .

Stock traders also seemed solidly against a shutdown . The Dow Jones Industrial Average fell by more than 120 points , or nearly 1 percent , and the other two major indexes also closed lower .

Among major economic issues that could result from a shutdown : delays in processing FHA housing loan applications -- a potential drag on the housing recovery -- and the potential loss of government spending that 's helping prop up the economy , said Christine Romans , host of CNN 's `` Your Money . ''

`` You 've got an economy right now that 's very tied to government spending and government contracts , so that could have a ripple effect all across Main Street , '' she said on CNN 's `` New Day . ''

If the government does shut down , it would be the first time it has happened in more than 17 years . That previous shutdown , sparked by a budget battle between Democratic President Bill Clinton and a Republican Congress , lasted for 21 days .

CNN Poll : GOP would bear the brunt of shutdown blame

While the military will remain on duty , as will many essential public safety , health and welfare operations , many government offices will close . About a quarter of the federal government 's 3.3 million employees -- those frequently referred to as `` nonessential '' -- will be told to stay home from work until the shutdown is over .

Attorney General Eric Holder and Defense Secretary Chuck Hagel said essential crime prevention and military services would continue , but some workers would be furloughed . Holder said he would cut his pay by the same amount as the most severely affected Justice Department employees because `` we are all in this together . ''

Meet the man behind the government shutdown

CNN 's Michael Pearson , Holly Yan , Lateef Mungin , Ted Barrett , Lisa Desjardins and Deirdre Walsh contributed to this report .

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NEW : The House is expected to vote again overnight , including on appointing House negotiators

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`` We will not go to conference with a gun to our head , '' says Sen. Harry Reid

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Obama says troops will get paid on time , but civilians may get more furloughs

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Conservatives wanted to undermine Obamacare before its private exchanges take effect Tuesday